Kawasaki KFX450R

On Oct 4, 2010

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With all the hoopla and fanfare over the new Yamaha 450X, the Kawasaki KFX450R is a big, green reality check. Yes, a fuel-injected, aluminum-frame, cross-country ATV with a full race identity is a big deal. But Kawasaki did it first. And the KFX still sets the bar pretty high.

The Kawasaki is a cross-country machine that has all the technology and performance that you usually find on full-race hardware. Just look at the MX Sports National MX series for proof of its effectiveness. The Monster Energy Kawasaki team won a number of races and had its best season ever.

Kawasaki doesn’t make separate quads for track and trail. The KFX450R is a race machine that has reverse and other amenities that make it one of the most versatile ATVs on the market.

WHAT IS IT?So in the real world, is the Kawasaki a motocrosser or a cross-country machine? These days, the difference is a little blurry, coming down to width and little else. But we consider the KFX more of a cross-country machine than any of the other Japanese 450s for one big reason: It has reverse. The Honda TRX450R can’t make that claim, and neither can the new Yamaha X or the admittedly track-oriented Suzuki R450. Plus, the Kawasaki’s width of 46.1 inches clearly puts it into the trail category, as do the tires and the super-quiet exhaust.

It’s clear, though, that the KFX was designed with racing in mind. That much is clear from its heritage and accomplishments. The motor is based on the same unit that powers the KX450 motocrosser, which is state-of-the-art in the motorcycle world. It’s a double overhead cam, four-valve, five-speed with fuel injection. Unlike the motorcycle, the KFX has an electric starter and the accompanying battery, which are items that you could remove if you wanted with the purchase of an optional kick-starter kit. Frankly, we think the electric starter is well worth the weight. It should be noted that Kawasaki’s wet weight figure of 395 pounds is wildly optimistic. The real weight is closer to 425, but fussing with such figures is common in the world of ad hype. The machine is still doing well considering the starter, reverse, the electric fan, lights and the enormous steel EPA and CARB-approved muffler.

Kawasaki sells one configuration of the machine in all states. There isn’t that much of a difference anymore between California specs and national ones, so it doesn’t make sense to make two versions. That means everyone gets a very clean, quiet machine. In the days of carburetors, that would really kill performance. But fuel-injected motors have a built-in advantage. They can meet the standard without throttle stops and crazy-lean fuel mixtures. The Kawasaki has an open-loop system that adjusts itself for things like air density and temperature. It does not self-adjust for engine alterations of any kind, or even fuel grade. It has no way of knowing what you’ve done to it because there’s no oxygen sensor in the exhaust pipe; that would be what they call a closed-loop system. Still, Kawasaki engineers know that people like to futz with their machines. There’s enough leeway in the stock fuel map to install an aftermarket exhaust without having the mixture get too far off base.

We installed a Motoworks SR4 exhaust system and had great results once we removed the airbox lid. The Kawasaki EFI system required no reprogramming.

RACE TESTThe KFX has become the general purpose sport ATV in Kawasaki’s line. There are virtually no other sport machines on the corporate showroom, aside from the KFX700 V-twin, which is a massive cruiser. So the KFX has to fill a lot of squares, from trail riding to duning to racing.

The guys at Kawasaki were anxious to show us how versatile the machine is, so they invited us to ride a WORCS race with a nearly stock KFX—it had only the addition of DG nerf bars and a dead-man’s switch, as required by regulations. They showed up at Glen Helen with the machine, we showed up with our gear and then rode this years model for the first time when the gate dropped. The learning curve is steep when a race is happening all around you. For the details of the race itself, go to www.dirtwheelsmag.com. But when it was all over, we knew the Kawasaki much better than we would have otherwise.

In terms of power, the machine is good but not earth-shattering. With the massive exhaust system, you can’t hear the KFX running when there are quads with full-race exhausts all around you. Yet it didn’t give up much ground all the way to the first turn, arriving near the front. What’s most impressive about the Kawasaki motor is how clean it runs. There is no hiccuping, hesitation or popping. It never stalls or flames out. In terms of sheer power, you can throw a blanket over the Honda, Suzuki, Can-Am, Yamaha and Kawasaki 450s, with the KTM and the Polaris a step higher because of more free-flowing (louder) exhaust systems. First gear on the Kawasaki is good for the track, but a little tall for tight trail riding. After that, all the ratios are close, and on top the machine maxxes out just over 70 mph.

There’s crazy power locked up in that motor. It has the potential to be the fastest machine on the track.

It’s tough to fault the handling of the KFX. It really can do it all. In the WORCS race, it had to deal with whoops so big that it was like riding over a lot full of unsold Smart Cars. They were huge. But when the Kawasaki was lined up all straight, it would suck them up easily. When it wasn’t straight, the machine did require a lot of muscle to handle, but we expect that for a stock machine. It’s no lightweight.

Our biggest complaint centers around small stutter bumps entering turns. The Kawasaki has fairly quick steering, and it would give the rider a bit too much unwanted feedback. The tall front tires compounded the problem by bouncing too much. The best front suspension in the world is ineffective if the tires are bouncing like basketballs, which is why more racers go to lower profile tires like the ITP QuadCross Pros that Josh Creamer and the other Kawasaki racers use.

Once in the turn, the Kawasaki is great. It gives up only a little to wider, more track-oriented machines in flat turns, but makes it up in narrow sections or if line selection is difficult. The ability to miss ugly bumps can be a huge advantage. After the race, when we took the Kawasaki off-roading, we found that the sharp steering was very effective for dodging rocks and making quick adjustments even when you’re not quite prepared. When you throw in the fact that it has reverse, we really began to appreciate the KFX as a weekend recreation quad. Here’s a bike that can be raced in stock form, but it doesn’t force you to give up any creature comforts.

If you want to go any further than a pipe and airbox mods, you’ll need to alter the EFI mapping. The Motoworks FMI allows you to go richer or leaner in seven different modes. Contact Motoworks at (951) 587-9222.

BUMPING IT UPWe can’t leave anything alone. The power on the KFX is decent, but just knowing that there’s a 50-horsepower racer buried in there was making us crazy. After the race, we made a wish list of things to sharpen the performance. The exhaust is always the easiest place to look, provided you ride in an area where the increase in noise won’t cause problems. We installed a Motoworks SR4 full system, which is stainless steel, comes with a spark arrestor and sells for $549.99. The noise level went up to about 96 dB at 4000 rpm, but at first, horsepower gains were only moderate. It wasn’t until we removed the airbox lid that the motor really came to life. We were amazed. Power increased across the board, with the most impressive gain in the low-end and middle. It doesn’t do that much good to remove all that restriction from the exhaust if the engine can’t breathe.

We were surprised that the fuel injection mapping allowed us to make such significant changes without any fuel mixture problems. If you made similar modifications to a motor with a carb, you would have to rejet, and even the Suzuki R450 requires the use of a Yoshimura Cherry Bomb to alter the EFI. The Kawasaki required nothing. But we still wondered how much more power was locked up in there, so our next step was to install the Motoworks Fuel Management Interface ($279.99). This is one of the easiest EFI modifiers out there because it requires no laptop computer and installs in minutes. It already has a recommended map for the Kawasaki, presuming you have the SR4 exhaust installed and the airbox lid removed. If you do want to make your own map, you can do that, too, by using the plus and minus buttons to change the mixture in different ranges. It does not allow you to alter the spark advance. The result was a modest increase in throttle response. The motor just seemed more willing to run.

As we said, the fuel mixture is one of the Kawasaki’s strong points. With just the intake and exhaust changes that we made, the EFI controller was sort of an attempt at fixing a problem that we weren’t experiencing. It would be different if we had more engine modification on the agenda. With an increase in compression, for example, the Fuel Management Interface would be essential. For us, we decided to stop here. The Kawasaki had a great motor when we were through. It made a great trail machine and a decent racer. If we go back to the track, lower-profile tires will be the only modification necessary. It would be nice to bring it up to the same level as the Suzuki and Yamaha YFZ450R by increasing the width with a wider axle and A-arm, but that would compromise it off-road. No one wants to mess up a good thing, and the Kawasaki’s versatility is definitely a very good thing.